Plasmid-mediated AmpC in Klebsiella pneumoniae and Escherichia coli from septicaemic neonates: diversity, transmission and phenotypic detection

Objectives: Presence and dissemination of plasmid-mediated AmpC genes (pAmpCs) have made bacte-ria cephalosporin-resistant and assessment of their prevalence and diversity is essential. Coexistence of pAmpCs with New Delhi metallo-& beta;-lactamase (blaNDM) has facilitated their spread and NDM interferes with correct pAmpC phenotypic identification.Methods: Assessment of pAmpCs in different species and sequence types (STs), co-transmission with blaNDM and phenotypic detection were analysed among Klebsiella pneumoniae (n = 256) and Escherichia coli (n = 92) isolated from septicaemic neonates over 13 years.Results: pAmpCs were present in 9% (30/348) of strains, 5% in K. pneumoniae and 18% in E. coli . pAmpC genes (blaCMY and blaDHA) were detected, blaCMY-42 and blaDHA-1 variants being predominant. Strains were resistant to most antimicrobials tested. blaCMY and blaDHA were dominant among E. coli (14/17) and K. pneumoniae (9/13), respectively. pAmpC-bearing strains belonged to diverse STs, including epidemic K. pneumoniae ST11 and ST147. Some strains co-harboured carbapenemase genes, blaNDM (17/30) and blaOXA-48 (5/30). In 40% (12/30) of strains, pAmpC genes were transferred by conjugation, of which 8/12 exhibited co-transfer with blaNDM. pAmpCs were frequently found in replicons as follows: blaDHA-1 with IncHIB-M, blaCMY-4 with IncA/C, blaCMY-6 with IncA/C, and blaCMY-42 with IncFII. The combination disk-diffusion test correctly detected pAmpC in 77% (23/30) of pAmpC-bearing strains. However, correct detection of pAmpC was higher in strains that did not harbour blaNDM vs. those with blaNDM (85% vs. 71%).Conclusion: Presence of pAmpCs along with carbapenemases, linkage with multiple STs, and replicon types indicated their potential for spread. pAmpCs can go undetected in the presence of blaNDM; hence, regular surveillance is required.& COPY; 2023 The Author(s). Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Automated summary

The presence and dissemination of plasmid-mediated AmpC genes (pAmpCs) in bacteria have made them cephalosporin-resistant. This study analyzed the prevalence and diversity of pAmpCs in Klebsiella pneumoniae and Escherichia coli isolated from septicaemic neonates. The study found that pAmpCs were present in 9% of strains, with blaCMY-42 and blaDHA-1 variants being predominant. Some strains also co-harbored carbapenemase genes, blaNDM and blaOXA-48.